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armv7m: Extract "exception taken" code into functions

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Extract the code from the tail end of arm_v7m_do_interrupt() which
enters the exception handler into a pair of utility functions
v7m_exception_taken() and v7m_push_stack(), which correspond roughly
to the pseudocode PushStack() and ExceptionTaken().

This also requires us to move the arm_v7m_load_vector() utility
routine up so we can call it.

Handling illegal exception returns has some cases where we want to
take a UsageFault either on an existing stack frame or with a new
stack frame but with a specific LR value, so we want to be able to
call these without having to go via arm_v7m_cpu_do_interrupt().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
This commit is contained in:
Peter Maydell 2017-02-28 12:08:18 +00:00
parent 14790f730a
commit 39ae2474e3
1 changed files with 68 additions and 50 deletions
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118
target/arm/helper.c
View file

@ -6002,6 +6002,72 @@ static void switch_v7m_sp(CPUARMState *env, bool new_spsel)
}
}
static uint32_t arm_v7m_load_vector(ARMCPU *cpu)
{
CPUState *cs = CPU(cpu);
CPUARMState *env = &cpu->env;
MemTxResult result;
hwaddr vec = env->v7m.vecbase + env->v7m.exception * 4;
uint32_t addr;
addr = address_space_ldl(cs->as, vec,
MEMTXATTRS_UNSPECIFIED, &result);
if (result != MEMTX_OK) {
/* Architecturally this should cause a HardFault setting HSFR.VECTTBL,
* which would then be immediately followed by our failing to load
* the entry vector for that HardFault, which is a Lockup case.
* Since we don't model Lockup, we just report this guest error
* via cpu_abort().
*/
cpu_abort(cs, "Failed to read from exception vector table "
"entry %08x\n", (unsigned)vec);
}
return addr;
}
static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr)
{
/* Do the "take the exception" parts of exception entry,
* but not the pushing of state to the stack. This is
* similar to the pseudocode ExceptionTaken() function.
*/
CPUARMState *env = &cpu->env;
uint32_t addr;
armv7m_nvic_acknowledge_irq(env->nvic);
switch_v7m_sp(env, 0);
/* Clear IT bits */
env->condexec_bits = 0;
env->regs[14] = lr;
addr = arm_v7m_load_vector(cpu);
env->regs[15] = addr & 0xfffffffe;
env->thumb = addr & 1;
}
static void v7m_push_stack(ARMCPU *cpu)
{
/* Do the "set up stack frame" part of exception entry,
* similar to pseudocode PushStack().
*/
CPUARMState *env = &cpu->env;
uint32_t xpsr = xpsr_read(env);
/* Align stack pointer if the guest wants that */
if ((env->regs[13] & 4) && (env->v7m.ccr & R_V7M_CCR_STKALIGN_MASK)) {
env->regs[13] -= 4;
xpsr |= 0x200;
}
/* Switch to the handler mode. */
v7m_push(env, xpsr);
v7m_push(env, env->regs[15]);
v7m_push(env, env->regs[14]);
v7m_push(env, env->regs[12]);
v7m_push(env, env->regs[3]);
v7m_push(env, env->regs[2]);
v7m_push(env, env->regs[1]);
v7m_push(env, env->regs[0]);
}
static void do_v7m_exception_exit(CPUARMState *env)
{
uint32_t type;
@ -6063,37 +6129,11 @@ static void arm_log_exception(int idx)
}
}
static uint32_t arm_v7m_load_vector(ARMCPU *cpu)
{
CPUState *cs = CPU(cpu);
CPUARMState *env = &cpu->env;
MemTxResult result;
hwaddr vec = env->v7m.vecbase + env->v7m.exception * 4;
uint32_t addr;
addr = address_space_ldl(cs->as, vec,
MEMTXATTRS_UNSPECIFIED, &result);
if (result != MEMTX_OK) {
/* Architecturally this should cause a HardFault setting HSFR.VECTTBL,
* which would then be immediately followed by our failing to load
* the entry vector for that HardFault, which is a Lockup case.
* Since we don't model Lockup, we just report this guest error
* via cpu_abort().
*/
cpu_abort(cs, "Failed to read from exception vector table "
"entry %08x\n", (unsigned)vec);
}
return addr;
}
void arm_v7m_cpu_do_interrupt(CPUState *cs)
{
ARMCPU *cpu = ARM_CPU(cs);
CPUARMState *env = &cpu->env;
uint32_t xpsr = xpsr_read(env);
uint32_t lr;
uint32_t addr;
arm_log_exception(cs->exception_index);
@ -6151,31 +6191,9 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
return; /* Never happens. Keep compiler happy. */
}
armv7m_nvic_acknowledge_irq(env->nvic);
v7m_push_stack(cpu);
v7m_exception_taken(cpu, lr);
qemu_log_mask(CPU_LOG_INT, "... as %d\n", env->v7m.exception);
/* Align stack pointer if the guest wants that */
if ((env->regs[13] & 4) && (env->v7m.ccr & R_V7M_CCR_STKALIGN_MASK)) {
env->regs[13] -= 4;
xpsr |= 0x200;
}
/* Switch to the handler mode. */
v7m_push(env, xpsr);
v7m_push(env, env->regs[15]);
v7m_push(env, env->regs[14]);
v7m_push(env, env->regs[12]);
v7m_push(env, env->regs[3]);
v7m_push(env, env->regs[2]);
v7m_push(env, env->regs[1]);
v7m_push(env, env->regs[0]);
switch_v7m_sp(env, 0);
/* Clear IT bits */
env->condexec_bits = 0;
env->regs[14] = lr;
addr = arm_v7m_load_vector(cpu);
env->regs[15] = addr & 0xfffffffe;
env->thumb = addr & 1;
}
/* Function used to synchronize QEMU's AArch64 register set with AArch32